相关实验视频
Updated: Sep 11, 2025

07:46
Setting Limits on Supersymmetry Using Simplified Models
Published on: November 15, 2013
8.6K
搜索勒普顿-风味-紫色衰变模式B^{0}→K_{S}^{0}τ^{±}l^{}与哈德罗尼克B标记在贝尔和贝尔II
Physical review letters
|August 12, 2025
概括
这项研究寻找了罕见的B-meson衰变,破坏了勒普顿风味,特别是B0到KS0和轻色勒普顿. 没有发现证据,为这些衰变速率建立新的上限.
科学领域:
- 高能物理 高能物理
- 粒子物理学 粒子物理学
- 味道物理学的物理
背景情况:
- 勒普顿风味违规 (LFV) 是超越标准模型的新物理学的关键指标.
- 寻找B介质子的LFV衰变为标准模型提供了严格的测试.
- B0→K_S^0τ^±l^ (l=μ,e) 衰变是对新物理学贡献的敏感探测器.
研究的目的:
- 执行第一个搜索勒普顿-风味-紫色衰变模式B0→K_S^0τ^±l^.
- 对这些衰变的分支分数设置竞争性的上限.
- 通过寻找与标准模型预测的偏差来限制新的物理模型.
主要方法:
- 使用了来自Belle (711 fb^-1) 和Belle II (365 fb^-1) 实验的数据样本.
- 采用哈德龙B标记技术进行完整的B介质重建.
- 分析了对标记的B介质子反弹系统的信号衰变,考虑了各种tau衰变模式.
主要成果:
- 没有发现B0→K_S^0τ^±l^衰变的证据.
- 在 [0.8,3.6]×10^-5.5 范围内的分支分数上设置90%的置信水平上限.
- 这些结果为这些特定的LFV衰变模式提供了迄今为止最严格的极限.
结论:
- 信号的缺失对新物理模型的参数空间造成了约束.
- 未来使用更大的数据集进行分析将进一步提高对这些罕见衰变的敏感性.
- 这种搜索有助于不断努力发现超越标准模型的物理学.
相关概念视频
Types of Radioactivity
17.4K
The most common types of radioactivity are α decay, β decay, γ decay, neutron emission, and electron capture.
Alpha (α) decay is the emission of an α particle from the nucleus. For example, polonium-210 undergoes α decay:
Alpha (α) decay is the emission of an α particle from the nucleus. For example, polonium-210 undergoes α decay:
17.4K
Nuclear Stability
19.8K
Protons and neutrons, collectively called nucleons, are packed together tightly in a nucleus. With a radius of about 10−15 meters, a nucleus is quite small compared to the radius of the entire atom, which is about 10−10 meters. Nuclei are extremely dense compared to bulk matter, averaging 1.8 × 1014 grams per cubic centimeter. If the earth’s density were equal to the average nuclear density, the earth’s radius would be only about 200 meters.
To hold positively charged protons together...
To hold positively charged protons together...
19.8K
Fermi Level Dynamics
341
The vacuum level denotes the energy threshold required for an electron to escape from a material surface. It is usually positioned above the conduction band of a semiconductor and acts as a benchmark for comparing electron energies within various materials.
Electron affinity in semiconductors refers to the energy gap between the minimum of its conduction band and the vacuum level and it is a critical parameter in determining how easily a semiconductor can accept additional electrons.
The work...
Electron affinity in semiconductors refers to the energy gap between the minimum of its conduction band and the vacuum level and it is a critical parameter in determining how easily a semiconductor can accept additional electrons.
The work...
341
Atomic Nuclei: Larmor Precession Frequency
1.7K
The earth's gravitational field produces a 'twisting force' perpendicular to the angular momentum of a spinning mass (such as a spinning top) that causes the mass to 'wobble' around the gravitational field axis in a phenomenon called precession. Similarly, the magnetic moment (μ) of a spinning nucleus precesses due to an external magnetic field directed along the z-axis. The precession of the magnetic moment vector about the magnetic field is called Larmor precession,...
1.7K
Atomic Nuclei: Nuclear Spin State Population Distribution
1.2K
Near absolute zero temperatures, in the presence of a magnetic field, the majority of nuclei prefer the lower energy spin-up state to the higher energy spin-down state. As temperatures increase, the energy from thermal collisions distributes the spins more equally between the two states. The Boltzmann distribution equation gives the ratio of the number of spins predicted in the spin −½ (N−) and spin +½ (N+) states.
1.2K
Deactivation Processes: Jablonski Diagram
887
Luminescence, the emission of light by a substance that has absorbed energy, is a process that involves the interaction of molecules with light. The energy-level diagram, or Jablonski diagram, is a graphical representation of these interactions, illustrating the various states and transitions a molecule can undergo. In a typical Jablonski diagram, the lowest horizontal line represents the ground-state energy of the molecule, which is usually a singlet state. This state represents the energies...
887

